1. Field of the Invention
The invention relates to a differential for a vehicle, and more particularly to a differential for a vehicle including a pinion gear shaft for preventing falling of a pinion gear which receives a rotation driving force from a drive side.
2. Description of Related Art
Heretofore, with regard to the prior art in this technical field, a differential for a vehicle as shown in FIG. 15 is known. This differential for a vehicle, for example, is described in Utility Model Registration No. 2,520,728 (refer to FIG. 1). This differential for a vehicle will now be described with reference to FIG. 15. Referring to FIG. 15, the differential 71 for a vehicle includes a differential case 72 which rotates by receiving an engine torque, side gears 73L and 73R which are provided in parallel with each other along an axis line of rotation of the differential case 72, and a pinion gear 74 which is engaged with each of the side gears 73L and 73R.
The differential case 72 is provided with a pinion gear insertion hole 75, and axle insertion holes 76L and 76R. Here, an axis line of the pinion gear insertion hole 75, and each of axis lines of the axle insertion holes 76L and 76R are at right angles to each other. In addition, the differential case 72 is provided with a recess groove 78 which is formed in an inner surface of the pinion gear insertion hole 75 and to which a snap ring 77 is fitted.
The side gears 73L and 73R are constituted by unbottomed cylindrical bevel gears which have a boss portion 79L and a gear portion 80L, and a boss portion 79R and a gear portion 80R, respectively. Also, the side gears 73L and 73R are disposed so as to be movable in the axis line of rotation of the differential case 72, and are supported rotatably within the differential case 72 so that the boss portions 79L and 79R face the axle insertion holes 76L and 76R, respectively. Axles 81L and 81R are spline-fitted into the side gears 73L and 73R, respectively, with parts of the axles 81L and 81R positioned within the axle insertion holes 76L and 76R, respectively. Annular sliding members 82L and 82R which are located in the circumstances of the boss portions 79L and 79R, respectively, are interposed between the gear portion 80L (back surface) of the side gear 73L, and an inner opening periphery of the axle insertion hole 76L, and between the gear portion 80R (back surface) of the side gear 73R, and an inner opening periphery of the axle insertion hole 76R, respectively.
The pinion gear 74 is constituted by an unbottomed cylindrical bevel gear. Also, the pinion gear 74 is retained by a pinion gear holding plate 83 interposed between the snap ring 77 and the pinion gear 74, and is rotatably supported within the pinion insertion hole 75. A pinion gear shaft 84 for preventing gear falling is inserted through a center of an axle of the pinion gear 74.
With the construction described above, when a torque is inputted from an engine side of the vehicle to the differential case 72 through a drive pinion and a ring gear, the differential case 72 rotates around the axis line of rotation. Next, when the differential case 72 rotates in such a manner, the rotating force is transmitted to the pinion gear 74, and moreover is transmitted from the pinion gear 74 to each of the side gears 73L and 73R. In this case, since the left-hand and right-hand axles are connected to the side gears 73L and 73R, respectively, through the spline fitting, the torque from the engine side is distributed depending on the driving situation of the vehicle to be transmitted to the left-hand and right-hand axles through the drive pinion, the ring gear, the differential case 72, the pinion gear 74, and the side gears 73L and 73R.